Gas turbine engine component coating with self-healing barrier layer

ABSTRACT

A method of providing a self-healing coating includes providing substrate, applying a layer of an aluminum-containing MAX phase material and another material to the substrate. The method includes exposing the layer to a temperature greater than 2000° F. to form alpha aluminum.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. application Ser. No. 15/036,885, filed May 16, 2016 which is a U.S. National Phase Application of PCT/US2014/064023 filed Nov. 5, 2014, which claims priority to U.S. Provisional Application No. 61/909,074, which was filed on Nov. 26, 2013 and is incorporated herein by reference.

BACKGROUND

This disclosure relates to a coating for components in applications such as gas turbine engines and internal combustion engines.

Many gas turbine engine components are subject to temperatures in excess of the melting temperature of the component substrate, which may be constructed from a nickel superalloy or non-oxide ceramic, for example. Cooling features and thermal barrier or environmental coatings are used to protect the substrate from these extreme temperatures.

Thermal barrier coatings (TBC) or environmental barrier coating (EBC) made from yttria-stabilized zirconia (YSZ) and gadolinium zirconium oxide are typically used to reduce the temperature of cooled turbine and combustor components. Additionally, these materials may also be used as abradable seal materials on cooled turbine blade outer air seals (BOAS) as well as other components. In these applications, there are several degradation and failure modes. During engine operation, thermal barrier coatings may become spalled, delaminated, chipped or eroded, for example, due to debris or environmental degradation.

Bond coats for thermal barrier coatings as well as environmental barrier coatings for high temperature composite materials rely on an oxygen diffusion barrier layer that is often alpha alumina. Alpha alumina is an excellent barrier to oxygen diffusion and naturally forms at elevated temperature on aluminum rich alloys. This layer is often referred to as a thermally grown oxide (TGO). As this TGO layer grows with time and temperature it typically buckles and spalls off at which time it must regenerate, drawing further from the aluminum reserves of the host material by diffusion. As the aluminum gets depleted, non-ideal oxides begin to form which make the TGO less effective at preventing further oxidation. Making TGO adhesion more difficult is the coefficient of thermal expansion (CTE) mismatch between the metallic aluminum donor and alumina layers during the thermal cycling present in most applications.

SUMMARY

In one exemplary embodiment, a method of providing a self-healing coating includes providing substrate, applying a layer of an aluminum-containing MAX phase material and another material to the substrate. The method includes exposing the layer to a temperature greater than 2000° F. to form alpha aluminum.

In a further embodiment of any of the above, the layer provides a MAX phase/metal matrix composite.

In a further embodiment of any of the above, the substrate is at least one of a nickel based alloy, an iron-nickel based alloy, a cobalt based alloy, a molybdenum based alloy, or a niobium based alloy.

In a further embodiment of any of the above, sing a thermal barrier coating is applied to the layer.

In a further embodiment of any of the above, the layer is a bond coat. The other material is at least one of a MCrAlY material (where M is nickel, iron and/or cobalt), an aluminide material, a platinum aluminide material, or a ceramic-based material.

In a further embodiment of any of the above, the aluminum-containing MAX phase material has an aluminum ratio of 0.6-1.4 times a stoichiometric aluminum value of the MAX phase material.

In a further embodiment of any of the above, the thermal barrier coating includes at least one of an yttria stabilized zirconia material and a gadolinia stabilized zirconia material.

In a further embodiment of any of the above, the substrate is a non-oxide ceramic including at least one of a ceramic based substrate or a ceramic matrix composite substrate.

In a further embodiment of any of the above, the non-oxide ceramic is SiC or SiN.

In a further embodiment of any of the above, the layer is an environmental barrier coating, and the other material is at least one of an alumina-containing ceramic, mullite, zircon, or rare earth silicates.

In a further embodiment of any of the above, the aluminum-containing MAX phase material has an aluminum ratio of 0.6-1.4 times a stoichiometric aluminum value of the MAX phase material.

In a further embodiment of any of the above, the metal matrix is formed from particles having a particle size of 0.02 and 0.5 microns.

In a further embodiment of any of the above, the particles of the metal matrix composite are formed via ball milling.

In a further embodiment of any of the above, the applying step comprises co-spraying individual constituent MAX phase and metal matrix composite particles.

In a further embodiment of any of the above, the MAX phase material has a particle size of between 1 and 3 microns.

BRIEF DESCRIPTION OF THE DRAWINGS

The disclosure can be further understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein:

FIG. 1 is a highly schematic view of a component with a self-healing bond coat supporting a thermal barrier coating.

FIG. 2 is a highly schematic view of a component with a self-healing environmental barrier coating supported on a substrate.

The embodiments, examples and alternatives of the preceding paragraphs, the claims, or the following description and drawings, including any of their various aspects or respective individual features, may be taken independently or in any combination. Features described in connection with one embodiment are applicable to all embodiments, unless such features are incompatible.

DETAILED DESCRIPTION

A component 10 is schematically shown in FIG. 1. The component 10, which may be a turbine blade airfoil, for example. The component 10 may be used in a variety of gas turbine engine components applications, including but not limited to vanes, blades, blade outer air seals, fuel nozzle guides, combustor liners, exhaust liners, and augmenter liners. The component 10 may be used in a variety of internal combustion engine component applications, such as exhaust manifolds, intake manifolds, valves, headers, turbo chargers, external waste gates, exhaust down pipes, exhaust systems, converters and mufflers.

The component 10 includes a substrate 12 that is formed from a material, such as a nickel based alloy, an iron-nickel based alloy, a cobalt based alloy, a molybdenum based alloy, or a niobium based alloy. A bond coat 14 is applied to the substrate 12, and a thermal barrier coating 16 is applied to the bond coat 14. The thermal barrier coating 16 has an exterior surface on a hot side of the component. In the example illustrated, the thermal barrier coating 16 is the outermost layer of the component 10 on a hot side of the component. Additional layers may be provided on the thermal barrier coating 16 covering the exterior surface, if desired.

The bond coat may be applied using any suitable technique known in the art. The bond coat 14 may be applied by low pressure plasma spray (LPPS), atmospheric plasma spray (APS), high velocity oxygen fuel (HVOF), high velocity air fuel (HVAF), physical vapor deposition (PVD), chemical vapor deposition (CVD) or cathodic arc, for example. Once the substrate surface is coated, the thermal barrier coating may be applied, for example, by using an electron beam physical vapor deposition (EBPVD) process, a suspension plasma spray (SPS), sputtering, sol gel, slurry, low pressure plasma spray (LPPS) or air plasma spray (APS), for example.

The thermal barrier coating 14 may comprise one or more layers of a ceramic material such as an yttria stabilized zirconia material, a gadolinia stabilized zirconia material, cubic/fluorite/pyrochlore/delta phase fully stabilized zirconates where stabilizers are any oxide or mix of oxides including Lanthanide series, Y, Sc, Mg, Ca, or further modified with Ta, Nb, Ti, Hf. The thermal barrier coating may also be hafnia based. The yttria stabilized zirconia material may contain from 3.0 to 40 wt. % yttria and the balance zirconia. The gadolinia stabilized zirconia material may contain from 5.0 to 99.9 wt. % gadolinia, and in one example, 30 to 70 wt. % gadolinia and the balance zirconia.

The bond coat 14 may be either a MCrAlY material (where M is nickel, iron and/or cobalt), an aluminide material, a platinum aluminide material, or a ceramic-based material. NiCoCrAlY bond coat and an yttria-stabilized zirconia (YSZ) thermal barrier coating may be used to provide the disclosed bond coat 14 and thermal barrier coating 16, for example. Of course, numerous other ceramic layers may be used. MCrAlY coatings also include MCrAlYX coatings, where X is at least one of a reactive element (Hf, Zr, Ce, La, Si) and/or refractory element (Ta, Re, W, Nb, Mo).

In addition to the above bond coat materials, the bond coat 14 includes a MAX phase material, which forms a MAX phase/metal matrix composite. A MAX phase material is a group of ternary carbides with the formula M_(n+1)AX_(n) (where n=1-3, M is an early transition metal, A is an A-group element and X is carbon and/or nitrogen). Desired MAX phase materials for the bond coat 14 include aluminum as the A-group element, which provides an aluminum rich source for thermally grown oxides having a high aluminum diffusion rate. Example MAX phase materials include Cr₂AlC, Ti₂AlC, Ti₂AlN and Ti₃AlC₂. Niobium-, tantalum- and vanadium-based MAX phase materials may also be used.

Aluminum-containing MAX phase materials having an extremely high diffusion rate of aluminum along the basal plane direction as well as provide phase stability of materials to as little as 0.6 of the stoichiometric aluminum ratio. One example desired amount of aluminum ratio in the MAX phase material is 0.6-1.4 the stoichiometric value, which provides high aluminum mobility. As a result, a bond coat 14 is provided that forms a high purity alumina TGO with rapid self-healing properties in temperatures above 2000° F. (1093° C.).

Example MAXMET (max phase/metal matrix composite) layer manufacturing methods include co-spraying of individual constituent MAX phase and metal matrix composite particles. The MAXMET particle size is, for example, 0.02 to 200 microns (0.00079 to 7.90 mils). MAX phase particles having a size of 1-3 microns (0.039 to 0.12 mils) are available as MAXTHAL powder from Sandvik Materials Technology. One method of producing the metal matrix composite particles is ball milling the constituents to mechanically alloy. This would produce a desirable distribution and size of 0.02 to 0.5 microns (0.0079 to 0.020 mils). The finer MAX phase particles result in a more homogeneous composite and provide optimal TGO growth uniformity.

The MAXMET material may be applied to the component by spraying the MAXMET particles by agglomeration, sintering, crushing of MAXMET, or atomization of a MAX particle suspension in a molten matrix (slush). Alternatively, a MAXMET preform may be manufactured and then bonded to the part by diffusion bonding or brazing. MAXMET may also be applied by directly forming the layer on the surface by hot pressing constituent powders or MAXMET particles.

Another component 18 is shown in FIG. 2. The substrate 20 is a non-oxide ceramic, such as a SiC or SiN ceramic based substrate or a ceramic matrix composite substrate. An environmental barrier coating 22 is applied to the substrate 20. The environmental barrier coating 22 may include an alumina containing ceramic, e.g., mullite, zircon (ZrSiO₄), rare earth silicates, combinations of at least one of the foregoing, and the like. Suitable rare earth silicates include, but are not limited to, yttrium silicate, yttrium disilicate, magnesium aluminate spinel, and the like.

The environment barrier coating 22 includes a MAX phase material as described above with respect to the bond coat 14.

The disclosed coating provides a higher purity and more stable alumina TGO layer than prior art oxidation resistant materials due to its improved ability to diffuse aluminum to the surface compared to prior art bond coat and aluminide materials. The MAX phase/metal matrix composite is highly damage tolerant, has reduced CTE mismatch with the TGO, larger aluminum reservoir and higher aluminum diffusion rates compared the prior art coatings.

It should also be understood that although a particular component arrangement is disclosed in the illustrated embodiment, other arrangements will benefit herefrom. Although particular step sequences are shown, described, and claimed, it should be understood that steps may be performed in any order, separated or combined unless otherwise indicated and will still benefit from the present invention.

Although the different examples have specific components shown in the illustrations, embodiments of this invention are not limited to those particular combinations. It is possible to use some of the components or features from one of the examples in combination with features or components from another one of the examples.

Although an example embodiment has been disclosed, a worker of ordinary skill in this art would recognize that certain modifications would come within the scope of the claims. For that reason, the following claims should be studied to determine their true scope and content. 

What is claimed is:
 1. A method of providing a self-healing coating, comprising: providing a substrate; applying a layer of an aluminum-containing MAX phase material and another material to the substrate; and exposing the layer to a temperature greater than 2000° F. to form alpha aluminum.
 2. The method according to claim 1, wherein the layer provides a MAX phase/metal matrix composite.
 3. The method according to claim 2, wherein the substrate is at least one of a nickel based alloy, an iron-nickel based alloy, a cobalt based alloy, a molybdenum based alloy, or a niobium based alloy.
 4. The method according to claim 2, comprising applying a thermal barrier coating to the layer.
 5. The method according to claim 4, wherein the layer is a bond coat, and the other material is at least one of a MCrAlY material (where M is nickel, iron and/or cobalt), an aluminide material, a platinum aluminide material, or a ceramic-based material.
 6. The method according to claim 4, wherein the aluminum-containing MAX phase material has an aluminum ratio of 0.6-1.4 times a stoichiometric aluminum value of the MAX phase material.
 7. The method according to claim 4, wherein the thermal barrier coating includes at least one of an yttria stabilized zirconia material and a gadolinia stabilized zirconia material.
 8. The method according to claim 2, wherein the substrate is a non-oxide ceramic including at least one of a ceramic based substrate or a ceramic matrix composite substrate.
 9. The method according to claim 8, wherein the non-oxide ceramic is SiC or SiN.
 10. The method according to claim 8, wherein the layer is an environmental barrier coating, and the other material is at least one of an alumina-containing ceramic, mullite, zircon, or rare earth silicates.
 11. The method according to claim 10, wherein the aluminum-containing MAX phase material has an aluminum ratio of 0.6-1.4 times a stoichiometric aluminum value of the MAX phase material.
 12. The method according to claim 2, wherein the metal matrix is formed from particles having a particle size of 0.02 and 0.5 microns.
 13. The method according to claim 12, wherein the particles of the metal matrix composite are formed via ball milling.
 14. The method according to claim 2, wherein the applying step comprises co-spraying individual constituent MAX phase and metal matrix composite particles.
 15. The method according to claim 1, wherein the MAX phase material has a particle size of between 1 and 3 microns. 